(1) Field of the Invention
The present invention relates generally to an apparatus for driving staples through tabs for securing sheet material to a substrate. In particular, the invention is well suited for efficiently securing roof felt to the roof of a structure.
(2) Decsription of the Prior Art
The conventional method of attaching roofing felt to a roof is to use a large headed fastener commonly referred to as a felt nail or xe2x80x9cbutton capxe2x80x9d. A popular type of felt nail has a plastic disc for a head through which a brad or nail has been factory pre-positioned. The plastic disc head is circular and concave towards the roof surface. A roofer carries a supply of felt nails in a nail apron. After roof felt has been positioned and the roofer is ready to fasten the felt to the roof, he or she holds the roofing nail erect with two fingers beneath the plastic disc head. Normally, the roofer sets the felt nail with one blow of the hammer then drives the felt nail to its final seated position with a second blow.
To prevent foot injuries, manufacturers of plastic disc type felt nails do not rigidly fix the nail portion within the plastic disc. This allows the nail to deflect away and not penetrate the shoe of someone who accidentally steps on the nail. Unfortunately, since the plastic disc does not rigidly hold the nail or brad, the setting blow often results in a bent nail and perhaps injured fingers. Bent felt nails are often discarded, resulting in many fasteners being carelessly tossed about.
Considering the wasted time and wasted felt nails littering the ground around roofed structures, it is not surprising that attempts to improve the roof felt attaching process are ongoing. In recent years, electric or pneumatic staple and nail guns have been adapted for the roofing process.
One such staple or nail gun is described in U.S. Pat. No. 5,184,752 to Zylka et al. Zylka et al. describes a method and apparatus for feeding tabs or discs to an automatic staple or nail gun for the purpose of attaching roof felt to the substrate of a roof. The Zylka et al. apparatus is comprised of a commercially available pneumatic nail gun, with an upright canister to contain plastic discs that are forced downward by a spring. A carriage is positioned underneath the canister to shuttle one disc at a time from the canister to below the nails being driven. Upon actuation of the nail gun""s triggering mechanism, a nail is expelled with force penetrating a disc, roof felt and roof substrate.
Unfortunately, electric and pneumatic nail guns are expensive, heavy, bulky and usually encumbered with a lengthy power cord or pneumatic hose. Worse still, power cords and or pneumatic hoses strewn across a roof become dangerous tripping hazards to workers on a roof. What is needed is an apparatus suitable for efficiently, safely and economically attaching roof felt to a roof.
The present invention addresses this need by providing a modified manual hammer-type stapler that is particularly well suited for securely attaching roof felt to a roof.
Hammer-type staplers are well known in the prior art, and are generally comprised of a staple delivery head and staple magazine attached to a handle. All hammer-type staplers generally fall into one of two categories. In the first category, a staple driver element is fixed to the staple delivery head and handle, with the staple magazine moving upward to meet the fixed staple driver element upon impact. In the second category, the staple delivery head and staple magazine are fixed. A staple is driven when the staple driver element is moved downward along a path to meet the lead staple from a magazine in response to impact.
The present invention includes modifications of a hammer-type stapler that falls within this second category. U.S. Pat. No. 2,896,210 to Rubin discloses an example of a second category stapler that can be suitably modified for use in the present invention. The Rubin patent discloses a hammer-type stapler having a staple magazine with a channel pathway that holds a strip of aligned, adjacent staples, along with a staple positioner that urges the staple strip to a discharge end of the magazine. A driver blade forces the leading staple of the strip through a staple exit when a striker connected to the driver blade by levers impacts a solid yet penetrable surface.
Roofers use hammer-type staplers to fasten roof felt onto a roof by impacting the roof felt stretched across the roof substrate with a hammer-like blow that drives the sharp pointed legs of a staple through the roof felt and into a roof substrate, usually made of wood. However, the use of staples alone as roof felt fasteners is adequate only in calm wind conditions. During windy conditions, roof felt has a tendency to rip away from the roof substrate leaving the staple behind.
A staple by itself does not have enough surface area to reliably hold fast the roof felt in breezy conditions. Waiting for calm wind conditions is not a viable option for roofers in an economic sense.
One known way of improving a staple""s fastening effectiveness is to increase the staple""s effective holding area by first driving the staple through a narrow strip of high tensile strength sheet material such as plastic or metal. Preferably, the sheet material is made from polystyrene plastic. Other suitable plastics include but are not limited to: Nylon, Lexan, acrylics, and polycarbonates.
This narrow strip of plastic or metal, commonly referred to as a tab, has substantially more surface area in contact with stapled material than a staple would alone. Consequently, a staple used in conjunction with a tab is significantly more effective as a fastener, so much more, that roof felt can be attached to a roof in wind conditions that would normally render the roof felting process futile. Prior art hammer-type staplers, however, do not include a means for feeding tabs under a stapler""s drive blade where tabs can be combined with staples in such a way as to increase the effective fastening capability of the staples.
The present invention addresses this need by providing a hammer-type stapler that includes a tab feeder. When the stapler of the present invention is struck against a roof surface covered by roof felt, a staple is driven into a plastic or metal tab that has an area substantially larger than the stable. With one blow of the hammer stapler, a staple is completely seated into the roof substrate with a tab on top and roof felt sandwiched between the tab and roof substrate. The relatively large area of the tab prevents the roofing felt from tearing away from the roof substrate even in windy conditions.
The hammer-type stapler of the present invention is generally comprised of a staple driver; an elongated handle extending rearwardly from the staple driver; a staple feeder parallel to and beneath the handle to position a staple beneath the staple driver; and a tab feeder parallel to and beneath the staple feeder to position a tab beneath the staple driver, so that a staple driven by the staple driver will penetrate the tab.
The staple driver includes a staple driver blade that is movable along a pathway between a raised and a lowered position, and a striker that is located at the distal end of the stapler and moveable upward when the striker impacts a surface to be stapled. A lever mechanism connects the striker to the driver blade, so that the driver blade moves downward when the striker is impacted against a surface. A return spring is connected to the lever mechanism to return the driver blade to the raised position when the stapler is lifted from the surface.
An elongated handle extends rearwardly from the staple driver for use in swinging the stapler. A grip, such as a molded plastic grip, may form part of the handle.
A staple magazine is positioned beneath, and parallel to, the handle to hold a plurality of staples that are fed sequentially beneath the drive blade of the staple driver. The staple magazine includes a discharge end that is adjacent the driver blade pathway, so that the lead staple is positioned against a stop for engagement by the driver blade as the blade is moved from its raised to its lowered position. A spring urges the staples against the stop.
A tab magazine is positioned beneath and parallel to the staple magazine. The tab magazine also has a discharge end adjacent to the driver blade pathway in order to position a tab beneath the driver blade, so that a staple driven by the driver blade will be driven through the tab before penetrating the surface. The tab magazine further comprises an elongated rectangular housing having a discharge end along with a spring to urge tabs within the housing towards the tab magazine""s discharge end. The tab magazine is adapted to move a planar strip of tabs along a tab pathway until the lead tab extends beyond the discharge end of the tab magazine and is stopped by a tab stop, which may be formed by the back edge of the striker.
The tab strip is comprised of a plurality of tabs that are joined to each other by perforations. The tabs preferably have a longitudinal dimension that is approximately equal to the distance between the discharge end of the tab magazine and the stop. Thus, the perforated edge between the leading and immediately trailing tabs will lie along the edge of the tab magazine discharge end, facilitating tearing of the leading tab from the tab strip.
When the striker of the hammer-type stapler impacts a hard yet penetrable surface, the staple driver will be moved from its raised to its lowered position, driving the lead staple through the tab beneath the staple and the surface of the material being stapled to a substrate. The legs of the driven staple continue through the material and sink into the substrate. As the stapler rebounds from impact the stapled tab is torn away from the tab strip along the perforated line. Once the driven staple and separated tab clear their respective magazines, a new staple and a new tab are forced against their respective stops. The tension springs of both the tab and staple magazines are sufficiently forceful to advance the next staple and the next tab quickly enough to be ready for the next staple blow no matter how often the roofer desires to drive a staple.
Consequently, a roofer using the present invention can be just as efficient as a roofer using an electric or pneumatic automatic stapler with tab feeder without having to contend with stringing dangerous power cords or hoses across a roof. Moreover, the hammer-type stapler of the present invention is much lighter, less bulky and less expensive than either electric or pneumatic automatic staple guns. Also, the hammer stapler outperforms the conventional hammer and felt nail method because there is no need for the roofer to manually hold the tab or plastic disc with one hand and hammer with the other. Furthermore, the hammer-type stapler of the present invention requires only one swing versus the conventional methods two.